fix: use original require() error for TS files if ERR_UNKNOWN_FILE_EXTENSION (#5408)

* fix: use original require() error if ERR_UNKNOWN_FILE_EXTENSION

* Update lib/nodejs/esm-utils.js

Co-authored-by: Mark Wiemer <[email protected]>

* Add in comments

* test: add broken-syntax.ts fixture and test

* chore: reset a change to main

* test: slightly improve name

---------

Co-authored-by: Mark Wiemer <[email protected]>

Author: JoshuaKGoldberg

lib/nodejs/esm-utils.js

@@ -101,9 +101,24 @@ const requireModule = async (file, esmDecorator) => {
     try {
       return dealWithExports(await formattedImport(file, esmDecorator));
     } catch (importErr) {
+      // If a --require module throws in a Node.js version that doesn't yet support .ts files,
+      // the fallback import() will throw an uninformative error about the file extension.
+      // What we actually care about is the original require() error.
+      // See: https://github.com/mochajs/mocha/issues/5393
+      if (
+        /\.(cts|mts|ts)$/.test(file) ||
+        importErr.code === 'ERR_UNKNOWN_FILE_EXTENSION'
+      ) {
+        throw requireErr;
+      }
+
+      // Similarly, for an exports/imports mismatch such as a missing 'default',
+      // the require() error will be more informative for users.
+      // See: https://github.com/mochajs/mocha/issues/5411
       if (importErr.code === 'ERR_INTERNAL_ASSERTION') {
         throw requireErr;
       }
+
       throw importErr;
     }
   }

test/node-unit/esm-utils.spec.js

@@ -20,6 +20,21 @@ describe('esm-utils', function () {
         }
       );
     });
+
+    it('should show a syntax error message when importing a TypeScript file with invalid syntax', async function () {
+      return expect(
+        () =>
+          esmUtils.requireOrImport(
+            '../../test/node-unit/fixtures/broken-syntax.ts'
+          ),
+        'to be rejected with error satisfying',
+        {
+          name: 'SyntaxError',
+          message:
+            /Invalid or unexpected token|Expected ident/
+        }
+      );
+    });
   });
 
   describe('loadFilesAsync()', function () {

test/node-unit/fixtures/broken-syntax.ts

@@ -0,0 +1 @@
+@!